The present invention relates to optical scanning devices.
Optical scanners are employed to scan a visible image such as a text image on a paper or other print medium, a photograph, negative, or transparency, and provide an electronic version of the scanned image suitable for copying, storing or processing by a computer. A reflective optical scanner typically has a controlled source of illumination light which is reflected off the surface of a document onto an array of photosensitive elements, i.e. an optical sensor. The sensor converts the received light intensity into an electronic signal. Transparency scanners pass illumination light through a transparent image such as a photographic positive slide or negative film image and then onto an optical sensor.
It would be advantageous to provide a technique for utilizing a reflective scanner to optically scan a transparent image.
One known technique for transparency scanning involves turning the internal light source off and turning on an external light source to backlight the transparent film. This solution requires the external light source, cabling and power source and these additional elements add to the cost. Another technique is to use a reflecting xe2x80x9ctentxe2x80x9d structure to reflect light from the internal light source over the top and down through the transparent media. This second approach, although being much less expensive than the first approach, can suffer from an optical flare problem. The primary light source not only gets projected over and down through the transparent media but also directly illuminates the underside of the media resulting in optical flare and degraded image quality.
In accordance with an aspect of this invention, an optical scanner system is described, wherein the central region of the light source is selectively covered up by a mechanically actuated shutter during a transparency scanning mode. By occluding the central portion of the light source the aforementioned problems with flare and degraded image quality are eliminated.
By eliminating external light source and its related power supply etc. a considerable cost savings can be realized while achieving the same quality image that can be achieved with the external light source components by means of this shutter. In accordance with a further aspect of the invention, the shutter is actuated to its two positions (normal reflective mode position, transparency mode position) by pins, protrusions, or the scanner walls in the scan module path. When the scan module is driven to the extremes of its travel the shutter is either driven open or closed.
A bracket structure is provided to hold the transparent media and the covering light reflective tent. This bracket structure can include a pin or pins that can protrude into the scanner module path and thus actuate the shutter only when the structure is mounted on to the scanner by the user. This bracket structure can include a lower member that rests directly on the glass to align filmstrips, slides, and other transparent media and which also holds the actuating pins. The bracket can also have an upper tent structure that is hinged relative to the lower structure which allow it to be opened and closed to enable insertion of transparent media. When the upper structure is closed it acts as the reflective light path to allow light from the primary light source to be reflected up, over, and down through the transparent media, and into the optical light path leading to the optical sensor.